1. Field of the Invention
The present invention relates generally to apparatus and methods for magnetic propulsion, and more particularly to an apparatus and method for reducing inductive coupling between levitation and drive coils within a magnetic propulsion system.
2. Discussion of Background Art
Magnetic levitation and propulsion systems of one sort or other have been in development for some time. As is well known, these systems use electromagnetic principles to generate magnetic fields which support and/or create motion without direct physical contact between a track of some sort and an object being supported and/or propelled.
For instance, in one type of "maglev" train, electrically powered magnet coils are used to produce a levitation force, and complex control circuits are needed to maintain the separation between the poles of these magnets and the under surface of a steel guide-way from which the levitation forces are produced. The control circuitry must be highly reliable, accurate, and responsive, due to the high speeds at which such trains are designed to operate. Other Maglev systems use superconducting coils, the magnetic fields of which interact with coils in a guide-way to produce levitation. These Maglev systems thus typically come with very high manufacturing, operation, and maintenance costs.
An alternative to "maglev" technology is presented in U.S. Pat. No. 5,722,326, entitled "Magnetic Levitation System for Moving Objects," by Richard F. Post, and assigned to The Regents of the University of California, Oakland, Calif. The '326 patent describes a less costly levitation and propulsion system incorporating a track containing an array of levitation and drive coils interacting with permanent-magnet bars arranged in a "Halbach Array" that are affixed to an object to be levitated and moved.
Application of the '326 patent's technology to high-speed trains as well as new uses such as launching objects into space and various low speed people mover and mining car applications often requires high acceleration rates. Such high acceleration rates are achieved by sending large current pulses through the drive coils. Since the drive coils are interleaved with the levitation coils, current changes in the drive coils will induce parasitic current fluctuations in the levitation coils, through mutual inductive coupling. These parasitic currents can interfere with normal levitation coil currents, resulting in reduced levitation and drive performance.
In response to the concerns discussed above, what is needed is an apparatus and method for magnetic propulsion which overcomes the problems of the prior art.